Warm the oil in a wide pot over medium heat.
Add onion and a pinch of salt; cook until softened, 5 minutes.
Stir in ginger and garlic; cook until fragrant, 1 minute.
Sprinkle in all spices; stir constantly to bloom, 30 seconds.
Add cauliflower; toss to coat in spices, about 2 minutes.
Pour in tomatoes and broth. Add salt and pepper. Bring to simmer.
Cover and cook, stirring sometimes, until cauliflower is tender, 12 to 15 minutes.
Stir in coconut milk and peas; simmer uncovered until slightly thickened, 3 to 4 minutes.
Stir in lemon juice and cilantro; taste and adjust seasoning.
Serve hot over rice or with warm naan.